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root/jsr166/jsr166/src/jsr166y/Phaser.java

Comparing jsr166/src/jsr166y/Phaser.java (file contents):
Revision 1.54 by dl, Sat Nov 13 13:10:04 2010 UTC vs.
Revision 1.59 by dl, Sat Nov 27 16:46:53 2010 UTC

#	Line 79 | Line 79 | import java.util.concurrent.locks.LockSu
79		* immediately return without updating phaser state or waiting for
80		* advance, and indicating (via a negative phase value) that execution
81		* is complete.  Termination is triggered when an invocation of {@code
82	<	* onAdvance} returns {@code true}.  As illustrated below, when
82	>	* onAdvance} returns {@code true}. The default implementation returns
83	>	* {@code true} if a deregistration has caused the number of
84	>	* registered parties to become zero.  As illustrated below, when
85		* phasers control actions with a fixed number of iterations, it is
86		* often convenient to override this method to cause termination when
87		* the current phase number reaches a threshold. Method {@link
88		* #forceTermination} is also available to abruptly release waiting
89		* threads and allow them to terminate.
90		*
91	<	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e., arranged
92	<	* in tree structures) to reduce contention. Phasers with large
93	<	* numbers of parties that would otherwise experience heavy
91	>	* <p> <b>Tiering.</b> Phasers may be <em>tiered</em> (i.e.,
92	>	* constructed in tree structures) to reduce contention. Phasers with
93	>	* large numbers of parties that would otherwise experience heavy
94		* synchronization contention costs may instead be set up so that
95		* groups of sub-phasers share a common parent.  This may greatly
96		* increase throughput even though it incurs greater per-operation
#	Line 240 | Line 242 | public class Phaser {
242		*/
243		private volatile long state;
244
245	<	private static final int  MAX_COUNT      = 0xffff;
246	<	private static final int  MAX_PHASE      = 0x7fffffff;
247	<	private static final int  PARTIES_SHIFT  = 16;
248	<	private static final int  PHASE_SHIFT    = 32;
249	<	private static final long UNARRIVED_MASK = 0xffffL;
250	<	private static final long PARTIES_MASK   = 0xffff0000L;
251	<	private static final long ONE_ARRIVAL    = 1L;
252	<	private static final long ONE_PARTY      = 1L << PARTIES_SHIFT;
253	<	private static final long TERMINATION_PHASE  = -1L << PHASE_SHIFT;
245	>	private static final int  MAX_PARTIES     = 0xffff;
246	>	private static final int  MAX_PHASE       = 0x7fffffff;
247	>	private static final int  PARTIES_SHIFT   = 16;
248	>	private static final int  PHASE_SHIFT     = 32;
249	>	private static final int  UNARRIVED_MASK  = 0xffff;      // to mask ints
250	>	private static final long PARTIES_MASK    = 0xffff0000L; // to mask longs
251	>	private static final long ONE_ARRIVAL     = 1L;
252	>	private static final long ONE_PARTY       = 1L << PARTIES_SHIFT;
253	>	private static final long TERMINATION_BIT = 1L << 63;
254
255		// The following unpacking methods are usually manually inlined
256
257		private static int unarrivedOf(long s) {
258	<	return (int) (s & UNARRIVED_MASK);
258	>	return (int)s & UNARRIVED_MASK;
259		}
260
261		private static int partiesOf(long s) {
262	<	return ((int) (s & PARTIES_MASK)) >>> PARTIES_SHIFT;
262	>	return (int)s >>> PARTIES_SHIFT;
263		}
264
265		private static int phaseOf(long s) {
#	Line 293 | Line 295 | public class Phaser {
295		}
296
297		/**
298	+	* Returns message string for bounds exceptions on arrival.
299	+	*/
300	+	private String badArrive(long s) {
301	+	return "Attempted arrival of unregistered party for " +
302	+	stateToString(s);
303	+	}
304	+
305	+	/**
306	+	* Returns message string for bounds exceptions on registration.
307	+	*/
308	+	private String badRegister(long s) {
309	+	return "Attempt to register more than " +
310	+	MAX_PARTIES + " parties for " + stateToString(s);
311	+	}
312	+
313	+	/**
314		* Main implementation for methods arrive and arriveAndDeregister.
315		* Manually tuned to speed up and minimize race windows for the
316		* common case of just decrementing unarrived field.
#	Line 303 | Line 321 | public class Phaser {
321		*/
322		private int doArrive(long adj) {
323		for (;;) {
324	<	long s;
325	<	int phase, unarrived;
326	<	if ((phase = (int)((s = state) >>> PHASE_SHIFT)) < 0)
324	>	long s = state;
325	>	int unarrived = (int)s & UNARRIVED_MASK;
326	>	int phase = (int)(s >>> PHASE_SHIFT);
327	>	if (phase < 0)
328		return phase;
329	<	else if ((unarrived = (int)(s & UNARRIVED_MASK)) == 0)
330	<	checkBadArrive(s);
331	<	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s -= adj)){
329	>	else if (unarrived == 0) {
330	>	if (reconcileState() == s)     // recheck
331	>	throw new IllegalStateException(badArrive(s));
332	>	}
333	>	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s-=adj)) {
334		if (unarrived == 1) {
314	–	Phaser par;
335		long p = s & PARTIES_MASK; // unshifted parties field
336		long lu = p >>> PARTIES_SHIFT;
337		int u = (int)lu;
338		int nextPhase = (phase + 1) & MAX_PHASE;
339		long next = ((long)nextPhase << PHASE_SHIFT) | p | lu;
340	<	if ((par = parent) == null) {
341	<	UNSAFE.compareAndSwapLong
342	<	(this, stateOffset, s, onAdvance(phase, u)?
343	<	next | TERMINATION_PHASE : next);
340	>	final Phaser parent = this.parent;
341	>	if (parent == null) {
342	>	if (onAdvance(phase, u))
343	>	next |= TERMINATION_BIT;
344	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
345		releaseWaiters(phase);
346		}
347		else {
348	<	par.doArrive(u == 0?
349	<	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
350	<	if ((int)(par.state >>> PHASE_SHIFT) != nextPhase ||
348	>	parent.doArrive((u == 0) ?
349	>	ONE_ARRIVAL|ONE_PARTY : ONE_ARRIVAL);
350	>	if ((int)(parent.state >>> PHASE_SHIFT) != nextPhase ||
351		((int)(state >>> PHASE_SHIFT) != nextPhase &&
352		!UNSAFE.compareAndSwapLong(this, stateOffset,
353		s, next)))
#	Line 339 | Line 360 | public class Phaser {
360		}
361
362		/**
342	–	* Rechecks state and throws bounds exceptions on arrival -- called
343	–	* only if unarrived is apparently zero.
344	–	*/
345	–	private void checkBadArrive(long s) {
346	–	if (reconcileState() == s)
347	–	throw new IllegalStateException
348	–	("Attempted arrival of unregistered party for " +
349	–	stateToString(s));
350	–	}
351	–
352	–	/**
363		* Implementation of register, bulkRegister
364		*
365	<	* @param registrations number to add to both parties and unarrived fields
365	>	* @param registrations number to add to both parties and
366	>	* unarrived fields. Must be greater than zero.
367		*/
368		private int doRegister(int registrations) {
369	<	long adj = (long)registrations; // adjustment to state
370	<	adj |= adj << PARTIES_SHIFT;
371	<	Phaser par = parent;
369	>	// adjustment to state
370	>	long adj = ((long)registrations << PARTIES_SHIFT) | registrations;
371	>	final Phaser parent = this.parent;
372		for (;;) {
373	<	int phase, parties;
374	<	long s = par == null? state : reconcileState();
375	<	if ((phase = (int)(s >>> PHASE_SHIFT)) < 0)
373	>	long s = (parent == null) ? state : reconcileState();
374	>	int parties = (int)s >>> PARTIES_SHIFT;
375	>	int phase = (int)(s >>> PHASE_SHIFT);
376	>	if (phase < 0)
377		return phase;
378	<	if ((parties = ((int)(s & PARTIES_MASK)) >>> PARTIES_SHIFT) != 0 &&
367	<	(s & UNARRIVED_MASK) == 0)
368	<	internalAwaitAdvance(phase, null); // wait for onAdvance
369	<	else if (parties + registrations > MAX_COUNT)
378	>	else if (registrations > MAX_PARTIES - parties)
379		throw new IllegalStateException(badRegister(s));
380	<	else if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
381	<	return phase;
380	>	else if ((parties == 0 && parent == null) || // first reg of root
381	>	((int)s & UNARRIVED_MASK) != 0) {   // not advancing
382	>	if (UNSAFE.compareAndSwapLong(this, stateOffset, s, s + adj))
383	>	return phase;
384	>	}
385	>	else if (parties != 0)               // wait for onAdvance
386	>	internalAwaitAdvance(phase, null);
387	>	else {                               // 1st registration of child
388	>	synchronized(this) {             // register parent first
389	>	if (reconcileState() == s) { // recheck under lock
390	>	parent.doRegister(1);    // OK if throws IllegalState
391	>	for (;;) {               // simpler form of outer loop
392	>	s = reconcileState();
393	>	phase = (int)(s >>> PHASE_SHIFT);
394	>	if (phase < 0 ||
395	>	UNSAFE.compareAndSwapLong(this, stateOffset,
396	>	s, s + adj))
397	>	return phase;
398	>	}
399	>	}
400	>	}
401	>	}
402		}
403		}
404
405		/**
406	<	* Returns message string for bounds exceptions on registration
378	<	*/
379	<	private String badRegister(long s) {
380	<	return "Attempt to register more than " +
381	<	MAX_COUNT + " parties for " + stateToString(s);
382	<	}
383	<
384	<	/**
385	<	* Recursively resolves lagged phase propagation from root if
386	<	* necessary.
406	>	* Recursively resolves lagged phase propagation from root if necessary.
407		*/
408		private long reconcileState() {
409		Phaser par = parent;
410	<	if (par == null)
411	<	return state;
412	<	Phaser rt = root;
413	<	for (;;) {
414	<	long s, u;
415	<	int phase, rPhase, pPhase;
416	<	if ((phase = (int)((s = state)>>> PHASE_SHIFT)) < 0 ||
417	<	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) == phase)
418	<	return s;
419	<	long pState = par.parent == null? par.state : par.reconcileState();
420	<	if (state == s) {
421	<	if ((rPhase < 0 || (s & UNARRIVED_MASK) == 0) &&
422	<	((pPhase = (int)(pState >>> PHASE_SHIFT)) < 0 ||
423	<	pPhase == ((phase + 1) & MAX_PHASE)))
424	<	UNSAFE.compareAndSwapLong
405	<	(this, stateOffset, s,
406	<	(((long) pPhase) << PHASE_SHIFT) |
407	<	(u = s & PARTIES_MASK) |
408	<	(u >>> PARTIES_SHIFT)); // reset unarrived to parties
409	<	else
410	<	releaseWaiters(phase); // help release others
410	>	long s = state;
411	>	if (par != null) {
412	>	Phaser rt = root;
413	>	int phase, rPhase;
414	>	while ((phase = (int)(s >>> PHASE_SHIFT)) >= 0 &&
415	>	(rPhase = (int)(rt.state >>> PHASE_SHIFT)) != phase) {
416	>	if ((int)(par.state >>> PHASE_SHIFT) != rPhase)
417	>	par.reconcileState();
418	>	else if (rPhase < 0 || ((int)s & UNARRIVED_MASK) == 0) {
419	>	long u = s & PARTIES_MASK; // reset unarrived to parties
420	>	long next = ((((long) rPhase) << PHASE_SHIFT) | u |
421	>	(u >>> PARTIES_SHIFT));
422	>	UNSAFE.compareAndSwapLong(this, stateOffset, s, next);
423	>	}
424	>	s = state;
425		}
426		}
427	+	return s;
428		}
429
430		/**
#	Line 434 | Line 449 | public class Phaser {
449		}
450
451		/**
452	<	* Creates a new phaser with the given parent, without any
453	<	* initially registered parties. If parent is non-null this phaser
454	<	* is registered with the parent and its initial phase number is
455	<	* the same as that of parent phaser.
452	>	* Creates a new phaser with the given parent, and without any
453	>	* initially registered parties.  Any thread using this phaser
454	>	* will need to first register for it, at which point, if the
455	>	* given parent is non-null, this phaser will also be registered
456	>	* with the parent.
457	>	*
458	>	* Equivalent to {@link #Phaser(Phaser, int) Phaser(parent, 0)}.
459		*
460		* @param parent the parent phaser
461		*/
#	Line 447 | Line 465 | public class Phaser {
465
466		/**
467		* Creates a new phaser with the given parent and number of
468	<	* registered unarrived parties. If parent is non-null, this phaser
469	<	* is registered with the parent and its initial phase number is
470	<	* the same as that of parent phaser.
468	>	* registered unarrived parties. If parent is non-null and
469	>	* the number of parties is non-zero, this phaser is registered
470	>	* with the parent.
471		*
472		* @param parent the parent phaser
473		* @param parties the number of parties required to trip barrier
#	Line 457 | Line 475 | public class Phaser {
475		* or greater than the maximum number of parties supported
476		*/
477		public Phaser(Phaser parent, int parties) {
478	<	if (parties < 0 || parties > MAX_COUNT)
478	>	if (parties >>> PARTIES_SHIFT != 0)
479		throw new IllegalArgumentException("Illegal number of parties");
480		int phase;
481		this.parent = parent;
#	Line 466 | Line 484 | public class Phaser {
484		this.root = r;
485		this.evenQ = r.evenQ;
486		this.oddQ = r.oddQ;
487	<	phase = parent.register();
487	>	phase = (parties == 0) ? parent.getPhase() : parent.doRegister(1);
488		}
489		else {
490		this.root = this;
#	Line 475 | Line 493 | public class Phaser {
493		phase = 0;
494		}
495		long p = (long)parties;
496	<	this.state = (((long) phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
496	>	this.state = (((long)phase) << PHASE_SHIFT) | p | (p << PARTIES_SHIFT);
497		}
498
499		/**
500	<	* Adds a new unarrived party to this phaser.
501	<	* If an ongoing invocation of {@link #onAdvance} is in progress,
502	<	* this method may wait until its completion before registering.
500	>	* Adds a new unarrived party to this phaser.  If an ongoing
501	>	* invocation of {@link #onAdvance} is in progress, this method
502	>	* may wait until its completion before registering.  If this
503	>	* phaser has a parent, and this phaser previously had no
504	>	* registered parties, this phaser is also registered with its
505	>	* parent.
506		*
507		* @return the arrival phase number to which this registration applied
508		* @throws IllegalStateException if attempting to register more
#	Line 495 | Line 516 | public class Phaser {
516		* Adds the given number of new unarrived parties to this phaser.
517		* If an ongoing invocation of {@link #onAdvance} is in progress,
518		* this method may wait until its completion before registering.
519	+	* If this phaser has a parent, and the given number of parities
520	+	* is greater than zero, and this phaser previously had no
521	+	* registered parties, this phaser is also registered with its
522	+	* parent.
523		*
524		* @param parties the number of additional parties required to trip barrier
525		* @return the arrival phase number to which this registration applied
#	Line 505 | Line 530 | public class Phaser {
530		public int bulkRegister(int parties) {
531		if (parties < 0)
532		throw new IllegalArgumentException();
533	<	if (parties > MAX_COUNT)
509	<	throw new IllegalStateException(badRegister(state));
510	<	if (parties == 0)
533	>	else if (parties == 0)
534		return getPhase();
535		return doRegister(parties);
536		}
537
538		/**
539		* Arrives at the barrier, but does not wait for others.  (You can
540	<	* in turn wait for others via {@link #awaitAdvance}).  It is an
541	<	* unenforced usage error for an unregistered party to invoke this
542	<	* method.
540	>	* in turn wait for others via {@link #awaitAdvance}).  It is a
541	>	* usage error for an unregistered party to invoke this
542	>	* method. However, it is possible that this error will result in
543	>	* an {code IllegalStateException} only when some <em>other</em>
544	>	* party arrives.
545		*
546		* @return the arrival phase number, or a negative value if terminated
547		* @throws IllegalStateException if not terminated and the number
#	Line 532 | Line 557 | public class Phaser {
557		* required to trip the barrier in future phases.  If this phaser
558		* has a parent, and deregistration causes this phaser to have
559		* zero parties, this phaser also arrives at and is deregistered
560	<	* from its parent.  It is an unenforced usage error for an
561	<	* unregistered party to invoke this method.
560	>	* from its parent.  It is a usage error for an unregistered party
561	>	* to invoke this method. However, it is possible that this error
562	>	* will result in an {code IllegalStateException} only when some
563	>	* <em>other</em> party arrives.
564		*
565		* @return the arrival phase number, or a negative value if terminated
566		* @throws IllegalStateException if not terminated and the number
#	Line 549 | Line 576 | public class Phaser {
576		* interruption or timeout, you can arrange this with an analogous
577		* construction using one of the other forms of the {@code
578		* awaitAdvance} method.  If instead you need to deregister upon
579	<	* arrival, use {@link #arriveAndDeregister}. It is an unenforced
580	<	* usage error for an unregistered party to invoke this method.
579	>	* arrival, use {@link #arriveAndDeregister}.  It is a usage error
580	>	* for an unregistered party to invoke this method. However, it is
581	>	* possible that this error will result in an {code
582	>	* IllegalStateException} only when some <em>other</em> party
583	>	* arrives.
584		*
585		* @return the arrival phase number, or a negative number if terminated
586		* @throws IllegalStateException if not terminated and the number
#	Line 575 | Line 605 | public class Phaser {
605		public int awaitAdvance(int phase) {
606		if (phase < 0)
607		return phase;
608	<	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
609	<	if (p != phase)
610	<	return p;
581	<	return internalAwaitAdvance(phase, null);
608	>	long s = (parent == null) ? state : reconcileState();
609	>	int p = (int)(s >>> PHASE_SHIFT);
610	>	return (p != phase) ? p : internalAwaitAdvance(phase, null);
611		}
612
613		/**
#	Line 599 | Line 628 | public class Phaser {
628		throws InterruptedException {
629		if (phase < 0)
630		return phase;
631	<	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
632	<	if (p != phase)
633	<	return p;
634	<	QNode node = new QNode(this, phase, true, false, 0L);
635	<	p = internalAwaitAdvance(phase, node);
636	<	if (node.wasInterrupted)
637	<	throw new InterruptedException();
638	<	else
639	<	return p;
631	>	long s = (parent == null) ? state : reconcileState();
632	>	int p = (int)(s >>> PHASE_SHIFT);
633	>	if (p == phase) {
634	>	QNode node = new QNode(this, phase, true, false, 0L);
635	>	p = internalAwaitAdvance(phase, node);
636	>	if (node.wasInterrupted)
637	>	throw new InterruptedException();
638	>	}
639	>	return p;
640		}
641
642		/**
#	Line 633 | Line 662 | public class Phaser {
662		public int awaitAdvanceInterruptibly(int phase,
663		long timeout, TimeUnit unit)
664		throws InterruptedException, TimeoutException {
636	–	long nanos = unit.toNanos(timeout);
665		if (phase < 0)
666		return phase;
667	<	int p = (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
668	<	if (p != phase)
669	<	return p;
670	<	QNode node = new QNode(this, phase, true, true, nanos);
671	<	p = internalAwaitAdvance(phase, node);
672	<	if (node.wasInterrupted)
673	<	throw new InterruptedException();
674	<	else if (p == phase)
675	<	throw new TimeoutException();
676	<	else
677	<	return p;
667	>	long s = (parent == null) ? state : reconcileState();
668	>	int p = (int)(s >>> PHASE_SHIFT);
669	>	if (p == phase) {
670	>	long nanos = unit.toNanos(timeout);
671	>	QNode node = new QNode(this, phase, true, true, nanos);
672	>	p = internalAwaitAdvance(phase, node);
673	>	if (node.wasInterrupted)
674	>	throw new InterruptedException();
675	>	else if (p == phase)
676	>	throw new TimeoutException();
677	>	}
678	>	return p;
679		}
680
681		/**
682	<	* Forces this barrier to enter termination state. Counts of
683	<	* arrived and registered parties are unaffected. If this phaser
684	<	* has a parent, it too is terminated. This method may be useful
685	<	* for coordinating recovery after one or more tasks encounter
686	<	* unexpected exceptions.
682	>	* Forces this barrier to enter termination state.  Counts of
683	>	* arrived and registered parties are unaffected.  If this phaser
684	>	* is a member of a tiered set of phasers, then all of the phasers
685	>	* in the set are terminated.  If this phaser is already
686	>	* terminated, this method has no effect.  This method may be
687	>	* useful for coordinating recovery after one or more tasks
688	>	* encounter unexpected exceptions.
689		*/
690		public void forceTermination() {
691	<	Phaser r = root;    // force at root then reconcile
691	>	// Only need to change root state
692	>	final Phaser root = this.root;
693		long s;
694	<	while ((s = r.state) >= 0)
695	<	UNSAFE.compareAndSwapLong(r, stateOffset, s, s | TERMINATION_PHASE);
696	<	reconcileState();
697	<	releaseWaiters(0); // signal all threads
698	<	releaseWaiters(1);
694	>	while ((s = root.state) >= 0) {
695	>	if (UNSAFE.compareAndSwapLong(root, stateOffset,
696	>	s, s | TERMINATION_BIT)) {
697	>	releaseWaiters(0); // signal all threads
698	>	releaseWaiters(1);
699	>	return;
700	>	}
701	>	}
702		}
703
704		/**
#	Line 674 | Line 709 | public class Phaser {
709		* @return the phase number, or a negative value if terminated
710		*/
711		public final int getPhase() {
712	<	return (int)((parent==null? state : reconcileState()) >>> PHASE_SHIFT);
712	>	return (int)(root.state >>> PHASE_SHIFT);
713		}
714
715		/**
#	Line 683 | Line 718 | public class Phaser {
718		* @return the number of parties
719		*/
720		public int getRegisteredParties() {
721	<	return partiesOf(parent==null? state : reconcileState());
721	>	return partiesOf(state);
722		}
723
724		/**
#	Line 731 | Line 766 | public class Phaser {
766		* @return {@code true} if this barrier has been terminated
767		*/
768		public boolean isTerminated() {
769	<	return (parent == null? state : reconcileState()) < 0;
769	>	return root.state < 0L;
770		}
771
772		/**
#	Line 756 | Line 791 | public class Phaser {
791		* {@code onAdvance} is invoked only for its root Phaser on each
792		* advance.
793		*
794	<	* <p>The default version returns {@code true} when the number of
795	<	* registered parties is zero. Normally, overrides that arrange
796	<	* termination for other reasons should also preserve this
797	<	* property.
794	>	* <p>To support the most common use cases, the default
795	>	* implementation of this method returns {@code true} when the
796	>	* number of registered parties has become zero as the result of a
797	>	* party invoking {@code arriveAndDeregister}.  You can disable
798	>	* this behavior, thus enabling continuation upon future
799	>	* registrations, by overriding this method to always return
800	>	* {@code false}:
801	>	*
802	>	* <pre> {@code
803	>	* Phaser phaser = new Phaser() {
804	>	*   protected boolean onAdvance(int phase, int parties) { return false; }
805	>	* }}</pre>
806		*
807		* @param phase the phase number on entering the barrier
808		* @param registeredParties the current number of registered parties
#	Line 795 | Line 838 | public class Phaser {
838		// Waiting mechanics
839
840		/**
841	<	* Removes and signals threads from queue for phase
841	>	* Removes and signals threads from queue for phase.
842		*/
843		private void releaseWaiters(int phase) {
844		AtomicReference<QNode> head = queueFor(phase);
#	Line 809 | Line 852 | public class Phaser {
852		}
853		}
854
812	–	/**
813	–	* Tries to enqueue given node in the appropriate wait queue.
814	–	*
815	–	* @return true if successful
816	–	*/
817	–	private boolean tryEnqueue(int phase, QNode node) {
818	–	releaseWaiters(phase-1); // ensure old queue clean
819	–	AtomicReference<QNode> head = queueFor(phase);
820	–	QNode q = head.get();
821	–	return ((q == null || q.phase == phase) &&
822	–	(int)(root.state >>> PHASE_SHIFT) == phase &&
823	–	head.compareAndSet(node.next = q, node));
824	–	}
825	–
855		/** The number of CPUs, for spin control */
856		private static final int NCPU = Runtime.getRuntime().availableProcessors();
857
#	Line 834 | Line 863 | public class Phaser {
863		* avoid it when threads regularly arrive: When a thread in
864		* internalAwaitAdvance notices another arrival before blocking,
865		* and there appear to be enough CPUs available, it spins
866	<	* SPINS_PER_ARRIVAL more times before continuing to try to
867	<	* block. The value trades off good-citizenship vs big unnecessary
868	<	* slowdowns.
866	>	* SPINS_PER_ARRIVAL more times before blocking. Plus, even on
867	>	* uniprocessors, there is at least one intervening Thread.yield
868	>	* before blocking. The value trades off good-citizenship vs big
869	>	* unnecessary slowdowns.
870		*/
871	<	static final int SPINS_PER_ARRIVAL = NCPU < 2? 1 : 1 << 8;
871	>	static final int SPINS_PER_ARRIVAL = (NCPU < 2) ? 1 : 1 << 8;
872
873		/**
874		* Possibly blocks and waits for phase to advance unless aborted.
#	Line 853 | Line 883 | public class Phaser {
883		boolean queued = false;      // true when node is enqueued
884		int lastUnarrived = -1;      // to increase spins upon change
885		int spins = SPINS_PER_ARRIVAL;
886	<	for (;;) {
887	<	int p, unarrived;
886	>	long s;
887	>	int p;
888	>	while ((p = (int)((s = current.state) >>> PHASE_SHIFT)) == phase) {
889		Phaser par;
890	<	long s = current.state;
891	<	if ((p = (int)(s >>> PHASE_SHIFT)) != phase) {
892	<	if (node != null)
893	<	node.onRelease();
863	<	releaseWaiters(phase);
864	<	return p;
865	<	}
866	<	else if ((unarrived = (int)(s & UNARRIVED_MASK)) != lastUnarrived) {
890	>	int unarrived = (int)s & UNARRIVED_MASK;
891	>	if (unarrived != lastUnarrived) {
892	>	if (lastUnarrived == -1) // ensure old queue clean
893	>	releaseWaiters(phase-1);
894		if ((lastUnarrived = unarrived) < NCPU)
895		spins += SPINS_PER_ARRIVAL;
896		}
#	Line 872 | Line 899 | public class Phaser {
899		par = par.parent;
900		lastUnarrived = -1;
901		}
902	<	else if (spins > 0)
903	<	--spins;
902	>	else if (spins > 0) {
903	>	if (--spins == (SPINS_PER_ARRIVAL >>> 1))
904	>	Thread.yield();  // yield midway through spin
905	>	}
906		else if (node == null)   // must be noninterruptible
907		node = new QNode(this, phase, false, false, 0L);
908		else if (node.isReleasable()) {
909	<	if ((int)(reconcileState() >>> PHASE_SHIFT) == phase)
909	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
910	>	break;
911	>	else
912		return phase;    // aborted
913		}
914	<	else if (!queued)
915	<	queued = tryEnqueue(phase, node);
914	>	else if (!queued) {      // push onto queue
915	>	AtomicReference<QNode> head = queueFor(phase);
916	>	QNode q = head.get();
917	>	if (q == null || q.phase == phase) {
918	>	node.next = q;
919	>	if ((p = (int)(root.state >>> PHASE_SHIFT)) != phase)
920	>	break;       // recheck to avoid stale enqueue
921	>	else
922	>	queued = head.compareAndSet(q, node);
923	>	}
924	>	}
925		else {
926		try {
927		ForkJoinPool.managedBlock(node);
#	Line 890 | Line 930 | public class Phaser {
930		}
931		}
932		}
933	+	releaseWaiters(phase);
934	+	if (node != null)
935	+	node.onRelease();
936	+	return p;
937		}
938
939		/**

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